#ifdef __KERNEL__
#include <linux/string.h>
#else
#include <string.h>
#endif
#include "modes_local.h"

#if defined(__GNUC__) && !defined(STRICT_ALIGNMENT)
typedef size_t size_t_aX __attribute((__aligned__(1)));
#else
typedef size_t size_t_aX;
#endif

/*
 * The input and output encrypted as though 128bit cfb mode is being used.
 * The extra state information to record how much of the 128bit block we have
 * used is contained in *num;
 */
void CRYPTO_cfb128_encrypt(const unsigned char* in, unsigned char* out,
                           size_t len, const void* key, unsigned char ivec[16],
                           int* num, int enc, block128_f block)
{
    unsigned int n;
    size_t       l = 0;

    n = *num;

    if (enc) {
        while (l < len) {
            if (n == 0) {
                (*block)(ivec, ivec, key);
            }
            out[l] = ivec[n] ^= in[l];
            ++l;
            n = (n + 1) % 16;
        }
        *num = n;
    } else {
        while (l < len) {
            unsigned char c;
            if (n == 0) {
                (*block)(ivec, ivec, key);
            }
            out[l]  = ivec[n] ^ (c = in[l]);
            ivec[n] = c;
            ++l;
            n = (n + 1) % 16;
        }
        *num = n;
    }
}

/*
 * This expects a single block of size nbits for both in and out. Note that
 * it corrupts any extra bits in the last byte of out
 */
static void cfbr_encrypt_block(const unsigned char* in, unsigned char* out,
                               int nbits, const void* key,
                               unsigned char ivec[16], int enc,
                               block128_f block)
{
    int           n, rem, num;
    unsigned char ovec[16 * 2 + 1]; /* +1 because we dereference (but don't
                                     * use) one byte off the end */

    if (nbits <= 0 || nbits > 128) return;

    /* fill in the first half of the new IV with the current IV */
    memcpy(ovec, ivec, 16);
    /* construct the new IV */
    (*block)(ivec, ivec, key);
    num = (nbits + 7) / 8;
    if (enc) /* encrypt the input */
        for (n = 0; n < num; ++n) out[n] = (ovec[16 + n] = in[n] ^ ivec[n]);
    else /* decrypt the input */
        for (n = 0; n < num; ++n) out[n] = (ovec[16 + n] = in[n]) ^ ivec[n];
    /* shift ovec left... */
    rem = nbits % 8;
    num = nbits / 8;
    if (rem == 0)
        memcpy(ivec, ovec + num, 16);
    else
        for (n = 0; n < 16; ++n)
            ivec[n] = ovec[n + num] << rem | ovec[n + num + 1] >> (8 - rem);

    /* it is not necessary to cleanse ovec, since the IV is not secret */
}

/* N.B. This expects the input to be packed, MS bit first */
void CRYPTO_cfb128_1_encrypt(const unsigned char* in, unsigned char* out,
                             size_t bits, const void* key,
                             unsigned char ivec[16], int* num, int enc,
                             block128_f block)
{
    size_t        n;
    unsigned char c[1], d[1];

    for (n = 0; n < bits; ++n) {
        c[0] = (in[n / 8] & (1 << (7 - n % 8))) ? 0x80 : 0;
        cfbr_encrypt_block(c, d, 1, key, ivec, enc, block);
        out[n / 8] = (out[n / 8] & ~(1 << (unsigned int)(7 - n % 8))) |
                     ((d[0] & 0x80) >> (unsigned int)(n % 8));
    }
}

void CRYPTO_cfb128_8_encrypt(const unsigned char* in, unsigned char* out,
                             size_t length, const void* key,
                             unsigned char ivec[16], int* num, int enc,
                             block128_f block)
{
    size_t n;

    for (n = 0; n < length; ++n)
        cfbr_encrypt_block(&in[n], &out[n], 8, key, ivec, enc, block);
}
